Assessing an object's consistency without touching it
(NCYT/CNRS) This technique, derived from the latest advances in nano-mechanics, has the advantage of being non-invasive and therefore non-destructive and could significantly improve the testing and analysis of thin, fragile objects such as bubbles or cells. This work is published on-line on June 18, 2012 on the website of the journal Physical Review Letters.
A simple way of determining whether a body is hard or soft is to touch it with a harder object. The problem with this technique is that it can destroy the item, especially if it is extremely fragile like a bubble or a living cell. Developing a less invasive alternative was therefore vital. To assess the rigidity of an object without touching it, the team of physicists had envisaged blowing on it delicately to check whether this flow of air deformed the material or not. But precisely controlling a flow of air is difficult on account of the vortexes that can form in the air. Hence the idea of using an easier-to-control "nano-flow" of fluid instead.
|Close up of the Pyrex sphere and Pyrex plane on which the nanometric scale elastic film is deposited. The small drop of liquid that serves as a probe is visible. (Photo: © Richard Villey and Frédéric Restagno)|
When the sphere comes up very close to the material (0.000001 meters), it pushes the liquid towards the object. This nano-flow generates a very slight pressure on the surface of the material. This force deforms the film very slightly, if it is flexible. On the other hand, if the tested object is completely rigid, the film remains unchanged.
The two teams also discovered that their method can be used to measure the rigidity of an array of bubbles, an element so fragile that touching it would mean destroying it! It is the first time that the possibility of measuring the elastic properties of an object using a nano-flow of fluid has been demonstrated. This initial work opens the way to a new nanometric-scale imaging technique for observing the elastic properties of very thin or thicker objects.
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